Field of the Invention
The present invention relates generally to the field of vibration testing of objects such as satellites, instrumentation or any other object whose reliability in operation may be evaluated using high intensity vibration testing. Specifically, the present invention relates to the use of direct field acoustic systems to perform vibration testing and to control means to increase the control bandwidth of direct field acoustic test systems having multiple outputs connected to separately driven groups of acoustical transducers.
Background of the Invention
The disclosure of co-pending U.S. application Ser. No. 13/117,870 filed May 27, 2011 is incorporated by reference herein in its entirety.
As disclosed in co-pending U.S. application Ser. No. 13/117,870 filed May 27, 2011 direct field acoustic test (DFAT) systems employing multiple separately controllable outputs driving separate groups of acoustic transducers have many advantages over prior art methods of performing acoustical vibration testing. However, the use of multiple separately controllable outputs connected to groups of separately driven acoustical transducers combined with the use of multiple microphones to provide separate control inputs leads to a geometric increase in the number and complexity of calculations required for real time control while a test is being performed. This in combination with the limitations of currently available hardware has placed certain limitations on the real time performance of multiple-input-multiple-output (MIMO) DFAT systems including limitations on the minimum frequency interval used for narrow band real time control, limitations on the maximum frequency for real time control to typically less than 2 kHz, limitations on the number of acoustical control inputs and separately controllable outputs as well as other limitations. In the performance of many types of acoustical vibration testing it is desirable to, for example, provide accurate control of the acoustic field at higher frequencies or use a larger number of control inputs and separately controlled outputs. Therefore it is desirable to provide a method of achieving faster real-time control of a MIMO DFAT system during closed loop operation.